Four friends travel to the gaming and carousing center of Las Vegas togive one of them a bachelor party on the eve of his wedding. What couldpossibly go wrong? As it turns out, just about everything does in abawdy but very funny new film. Here's a look at The Hangover.

It'sa road trip from Los Angeles to Las Vegas where best friends Stu andPhil along with future brother-in-law Alan plan to give Doug a rousingcelebration just before he gets married.

It starts with thepromise of fun and maybe even a bit of debauchery as they raise theirglasses in a toast to the groom; but things are quite different thenext morning. Their hotel suite looks like a tornado has ripped throughit: broken furniture, torn curtains, holes in the wall and, for somereason, a chicken cackling and strutting about.

Justin Bartha,Zach Galifianakis, Bradley Cooper and Ed Helms in scene from The HangoverThe three of them have no recollection whatsoever of the night before. Three of them? One is missing: the groom!

Sonow they have to retrace their steps, figure out what happened, findDoug and get him back home in time for the wedding, which is to takeplace that afternoon.

The ensemble cast of The Hangoverfeatures Justin Bartha as the misplaced groom and he says the comedygets more and more outrageous as the friends learn about theirwild-and-crazy night.

Justin Bartha as groom, Doug Billings in The Hangover"There are definitely moments where yousay 'this is shocking' and hilarious. This movie has a ton of thosemoments. It really does," Bartha says."There's a naked gangster thatjumps out of a trunk onto someone's shoulders, beats them up and thenruns away. I've never seen that in a movie …and I always have wantedto."

Ed Helms plays Stu who is a dentist so when he wakes up with a tooth missing he knows strange things must have gone on.

Ed Helms as Stu Price in The Hangover"Alot of things in the script were initially not explained and it's somuch fun to portray the aftermath of this night and let the audiencetry to put pieces together with our guys as they move through thestory," says Helms.

Among those pieces: Stu, who has a fiancéeback in Los Angeles, has somehow married a cheerful exotic dancer namedJade played by Heather Graham.

Heather Graham as Jade in The Hangover"I actually thought it was fun toplay such a colorful character and not just the 'sidekick' to theguys," Graham says. "I got to be this quirky character on my own and Imade up my own back-story where I was a spiritual new age stripper justtrying to share my sexuality with the world for the great goal ofspirituality."

Bradley Cooper is Phil, the groom Doug's best friend and organizer of the bachelor party, which turns into a frantic mystery.

Bradley Cooper as Phil Wenneck in The Hangover"That'sthe cool part of the movie," Cooper says. "If you like these threeguys together and you care about what they're doing then you're goingto go on the ride because you are in the exact same head space that theguys are in.

Rounding out the quartet is Zach Galifanakis as thegroom's quirky future brother-in-law. A veteran improvisational comic,Galifanakis says some of the funniest scenes were not originally in thescript.

"The outline of the movie was a very good blueprint, butany comedy director wants you to improvise and we did improvise a lot,"he says. "There were a lot of lines that were fine in the script butthings change when you shoot so you kind of go with the flow."

Thedirector is Todd Phillips, whose previous films include the hit OldSchool - another 'buddy' comedy - and he says it was important to makethe real Las Vegas environment part of "The Hangover" story.

Director Todd Phillips on the set of the movie"Ijust think comedy plays so much better when it plays against reality,so I always want it feel as organic as possible. If we're going toshoot in Caesars Palace I'd like to cut inside and be in theCaesars lobby," Phillips says. "I'd like to be shooting at Caesars poolor their valet (parking area). All of that stuff is really important."

The Hangover also features a cameo by boxer Mike Tyson along with several prominent Las Vegas celebrities.